The major objective of this case-control study is to learn more about the epidemiology of multiple myeloma (MM). Surprisingly little is known about the epidemiology of MM, available information is dated, and there are few etiologic hypotheses. To our knowledge, this will be the first case-control study specifically involving MM cases. The study will have 2 major components, a medical record review of 450 MM cases and an interview study of an additional 150 MM patients, both components involving matched hospital controls. In addition to examining for associations with available demographic variables, associations between MM and socio-economic class (S-E), occupation, environmental exposures, diet, and diseases causing "immune stimulation" will be evaluated. Particular attention will be paid to evaluation of the association between S-E class and MM. Paradoxically, MM is reported as being positively associated with high S-E class whereas incidence rates are twice as high in blacks than in whites.